Stock Repurchases (Details Textual) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended	12 Months Ended	100 Months Ended
	Jan. 31, 2020	Jul. 31, 2019	Jan. 31, 2020	Sep. 22, 2011
Stock Repurchased and Retired During Period, Shares		7,635,596
Stock Repurchased and Retired During Period, Value		$ 365.0
Stock Repurchased and Retired During Period Cost Per Share		$ 47.81
Remittance to taxing authorities under statutory withholding	$ 101.3
Number of stock options exercised	5,852,000
Stock Repurchase Program 2011
Stock Repurchase Program Additional Number Of Shares Authorized Approved				80,000,000
Stock Repurchased and Retired During Period, Shares			114,549,198
Number of shares available for repurchase under stock repurchase program	81,450,802		81,450,802
Common Stock | Stock Repurchase Program 2011
Common stock authorized for repurchase (in shares)				196,000,000